A new study suggests a link between women's eating low-fat yogurt during pregnancy to an increased risk that their children will develop asthma and hay fever.

The research, which will be presented at a meeting of the European Respiratory Society, drew on Danish birth and health records to study the dairy intake of more than 61,000 women and found that the children born to women who ate one or more low-fat fruit yogurts a day were more likely to develop asthma and hay fever than the children of women who didn't eat low-fat yogurt.

They also found that children of women who drank whole milk were at lower risk for developing asthma and hay fever than children of women who drank low-fat or skim milk.

Lead researcher Ekaterina Maslova at the Harvard School of Public Health said one reason for the association could be that certain fatty acids present in whole milk could offer a protective effect.

"[Some studies] have suggested that these fatty acids may be important for allergic disease development in humans," Maslova said in an email. Low-fat yogurt may not contain certain fatty acids believed to protect against asthma, she explained.

Despite the strong association, Maslova emphasized that the findings were only preliminary and didn't take other possible factors into account.

The study didn't account for the different types of dairy, so other active ingredients could be involved.

"We are also looking into the possibility that intake of low-fat yogurt may be a marker of other behaviors or lifestyle choices that may be driving these associations," said Maslova.

Fatty Acids Shown to Act on Immune System

Experts say other studies have looked at the role of fatty acids on immune system function.

"Giving omega-3 fatty acids to pregnant women seems to reduce the risk of asthma in children," said Dr. Erick Forno, a pediatric pulmonologist at the University of Miami's Miller School of Medicine. Omega-3 fatty acids are essential for the body's metabolism, but the human body doesn't make them. Common sources are fish oils and certain plant oils.

Conjugated linoleic acids, or CLAs, are fatty acids found in dairy products such as yogurt. Forno said research has found that CLAs are similar to omega-3 fatty acids in terms of their ability to protect against asthma.

"Fatty acids get metabolized and inhibit the production of another acid that gets converted into inflammatory molecules," he said.

Other experts also stress that these findings merely suggest an association and are very preliminary.

"There are a lot of unanswered questions. For example, we don't know if the women were taking omega-3 fatty acids or if they were eating highly processed yogurt," said Dr. Jana Klauer, a New York physician specializing in nutrition. Klauer explained these and other factors could account for the findings.

This research also does not change nutritional advice for pregnant women.

"It's recommended that pregnant women keep down the amount of calories and fat. They don't want to gain too much weight," said Klauer. "The current recommendation is low-fat dairy."